Biodiversity changes over time

• fossils have been dated and compared to determine which species were present at a certain time
• there are two techniques to date fossil:

  • relative dating is based on the age of the rock the fossil was found
  • numerical dating is measuring radioactivity of the minerals found in the specimen
• a rapid drop-off of species is regared as a mass exxtinction (mass extinction is when over 75% of species become extinct)
• change in ecological niches means new species evolve in their place
• roughly 5 times in the past 500 million years 75% to 90% of all species on earth have disappeared
• Ordovician-SIlurian extinction (444 million years ago):

  • major cooling event
  • Earth's watr was locked in an ice cap which menat seas were extremely shallow
  • killed about 85% of all species over 4 million years
• Late Devonian exticntion (383-359 million years ago):

  • ocean oxygen levels dropped
  • possibly caused by volcanic eruptions
  • plants evolved to get bigger and for the roots to go deeper
  • elimanated 75% of all species on Earth over roughly 20 million years
• Permian-Triassic extinction (252 million years ago):

  • major eruption event that released 13 trillion tonnes of carbon
  • global warming
  • rocks weathered rapidly due to acid rain
  • oceans may have lost 76% of available oxygen
  • 96% of all marine species and 3 out of 4 land species died over 60,000 years
• Triassic-Jurassic extinciton (201 million years ago):

  • Earth warmed 3-4 degress
  • possibly triggered by by an eruption
  • 80% of all land and marine species were lost over 18 million years
• Cretaceous-Palogene extinciton (66 million years ago):

  • an asteroid hit
  • large amounts of dust, rock and sulfur blocked out the sun
  • global cooling
  • 76% of all species on earth were lost over 32,000 years
• extinction today:

  • background extinction is usually 1 species per million per year but the rate is increasing
  • caused by human activities
• radpid diversification events seen ti be caused by tetonic plate movement
• natural changes occur over time the influence ecosystem diversification, species endemism, the formation of diversity hotspots and rate of extinction
• isolation is a risk to species as it can result in genetic drift, inbreeding, demographic variations, and/or a loss of genetic diversity which can lead to an inability to produce offspring
• first nations of Australia have used fire to accelerate plant germination and burn off over growth that may lead to more intense fire
• El Nino Southern Oscillation (ENSO) is where sea surface temperature variations affects the climate in different parts of the globe
• neutral state:

  • winds blow east to west
  • water in west Pacific Ocean is warmer than the east
• El Nino:

  • winds weaken or reverse
  • sea surface temperatures are warmer in the weat than the east
  • west experiences less rain
  • east experiences more rain
• La Nina:

  • increase warmth of water in west
  • more rain for Australia
• tectontic plate movemnt can cause volcanic eruptions and tsunamis
• marine species become more numnerous when continents divide
• short term disruptions to biodiversity occur when single events cause the death of organisms in an ecosystem
• key features of short term impacts:

  • usually minimal impacts on biodiversity
  • lastin gimpacts if a species becomes extinct
• key features of medium term impacts:

  • genetic and species diversity helps to maintain survival until regular conditions return
  • individuals and populations are likely to die out
  • vulnerable species could be pushed to extinction
• disruptions that result in the permanent changes to living conditions requires adaptations in order for species and ecosystems to continue
• key feature of long term impacts:

  • lasting changes in types of ecosystems in an area
• fossils = the ramains or impressions of a prehistoric organism embedded in rock and preserved in a petrified form
• rapid diversification = rapid increase in a number of species
• niche = the sum total of the environmental factors and interspecies relationships which influence a specie's survival
• endemic = a species that is restricted in geograpical distribution and is only found in one particular location
• biodiversity hotspot = an environment with a wide variety of life forms thst is currently under threat